ST25R3916 and ST25R3916B possible default analog config issue

[ryan1881]

I am currently using a mix of ST25R3916 and ST25R3916B with ST25RFAL002 v2.8.0.

In the default analog config table for the 3916 (rfalAnalogConfigTbl.h), under CHIP_INIT, there is an undocumented register that is being configured:

0x84U, 0x10, 0x10          /* Avoid chip internal overheat protection */

This does not appear in the default analog config table for the 3916B.  It seems like disabling overheat protection is probably not what is intended since I don't see anything in the errata about any issues with overheat protection.  That is just my assumption though, so I wanted to get some clarification on why this was being configured.

[Brian TIDAL]

Hi,

The setting 0x84U, 0x10, 0x10 is specific for the ST25R3916-nonB. See §2.4 in AN5584 ST25R39xx NFC reader thermal design for more information.

Rgds

BT

[ryan1881]

Ah, I see that now.  AN5584 makes it seem like setting that register is just for measuring driver resistance.  Does it need to be set for normal operation as well?

[Brian TIDAL · Accepted solution]

Hi,

the default ST25R3916-nonB analog configuration uses this internal overheat protection setting for normal operation. It should be kept if you have custom analog config.

Rgds

BT

[Ulysses HERNIOSUS]

Please see also DS12484 ch. 4.1: "To prevent the internal overheat protection to trigger below the junction temperature, the 3-byte frame FCh / 04h / 10h (register access / address / value) has to be sent after power-on and Set default command"

Regards, Ulysses